While there are a number of cool mods for Kubi in the Workshop, Somamint's Japan Mod really stands out when it comes to the sheer amount of content. It includes a new campaign, new biomes, many new resources and products to discover as well as changes to the game mechanics. The mod is still in beta at the moment but it is already really playable and fun. :)
You can find the full mod here:
https://steamcommunity.com/sharedfiles/filedetails/?id=2478958712